This invention relates generally to conveyor sortation systems and, in particular, to a positive displacement sorter of the pusher shoe and slat configuration.
Positive displacement sortation conveyors are known having a main conveying surface and diverter shoes that are generally used to displace articles laterally on the main conveying surface, such as when the articles are to be diverted upon one or more spur conveyor lines typically placed at an angle to the main conveying surface. Such conveyors may include a pair of endless chains and a plurality of members, such as slats, connected at their opposite ends to the chains in order to provide a moving conveyor surface. Each slat, or every other slat, is fitted with a pusher or diverter shoe mounted in a manner such that the shoe may glide laterally across the slat. Movement of the shoe is guided by a guide track beneath the conveying surface. At the loading end of the sortation system, the shoes have a particular orientation with respect to the conveying surface. When an article is to be diverted to a particular spur line, a diverter assembly is actuated to switch a portion of the shoes adjacent the article onto one or more diagonal tracks causing the effected shoes to glide across the slats to divert the article. Examples of such positive displacement sorters include commonly assigned U.S. Pat. Nos. 4,738,347 and 5,127,510. Other examples include U.S. Pat. Nos. 3,361,247; 5,409,095; and 4,884,677; and European Published Patent Applications EP 0 602 694 B1 and EP 0 444 734 A1.
In many instances, sortation conveyors are driven by rotary motors operatively connected to sprockets which propel the chains. As the application in which the sortation conveyors are used becomes increasing large, the size of the rotary motors must correspondingly increase in order to provide sufficient power to propel the longer conveying surface, as well as achieve the desired throughput. As the size of the motors and sprockets increases in order to meet the additional power requirements, the noise issued from the rotary motor, as well as the sizes of the sprockets and chains, correspondingly increase.
There is a long-felt need to increase the throughput of conveyor systems. Sortation conveyors and their associated induction conveyors are often the most challenging portion of the conveyor system to handle increasing demands for article throughput. Increase in throughput can be achieved by increasing the speed of the conveying surface. However, there are difficulties in continuously increasing the speed of the conveying surface. Another way to increase throughput is to decrease the gap between articles while ensuring sufficient gap to allow the articles to be properly diverted to their destination spur. As gaps get smaller to increase throughput, the necessity to maintain control over the gaps increases. Because gaps are established by placement of articles on the conveying surface of the sorter and the articles are placed on the conveying surface of the sorter from an induct conveyor, the requirement for smaller gaps increases the desirability to place and maintain the articles in proper position on the conveying surface of the sorter.